Lowell Franga is a long and avid supporter of The Light's Right community. I've used his photographs for two coaching sessions. This will be the third.

A word of warning up front! This coaching session will focus a lot on techniques that assume intermediate Photoshop experience. To gain the most from ths coaching session, you should be comfortable with the terminology and techniques for selections, masks, and compositing. You might want to read some basic information on HDR (High Dynamic Range), too.

Lowell sent me four photographs of the interior of a German church. St. Johannes der Taufer Sesslach. He asked me to show him how to use Photomatix to combine them into one photograph.

A church interior with bright light outside streaming through stained glass is a photographic challenge. It's a challenge for both film and digital. The problem is the dynamic range of the scene is very wide.

Let's take a quick look at Lowell's four exposures. He used a tripod and cable release to get multiple exposures with the camera remaining stationary. I'm guessing he did not use auto exposure bracketing (AEB) because the bracketing was a bit peculiar. -3 stops, 0 stops, +1 stop, and +2 stops.

The exposure at -3 stops was critical. It captured the stained glass without burning out significant detail. The interior is hopelessly underexposed. As a single, isolated exposure, it would be a disappointment. But the idea of HDR photography is to fuse together features from multiple photos. The HDR software the Lowell and I both use is Photomatix Pro and it can use a photo like this to hold detail in the stained glass.

Truth be told, I wasn't confident that the HDR software would hold as much detail as I would like. That's not a ding at Photomagtrix Pro. It's a general expectation with HDR software. We'll see below that my intuition was right. Photomatix was able to hold a lot of detail but the original retained more. And that's where this coaching session gets more complicated than running Photomatix and calling it a job well done.

Getting a good exposure for the interior of a church is always tricky with DSLRs. This is a bit dark, but the camera told Lowell it was correct. Even though the interior is still subdued, the stained glass windows are losing highlight details. The interior will lighten to provide more photographic details as the exposure increases and, of course, more and more detail in the stained glass will be lost.

Extending the Dynamic Range

HDR software like Photomatix Pro can extend the details in the highlights and the shadows by processing multiple exposures to make one since HDR image. Photoshop CS4 also includes HDR support, but the commercial tools for HDR are more flexible and more powerful.

Photomatix offers two methods for blending together exposures to extend dynamic range: HDR tone mapping and exposure blending. For this coaching session, I chose HDR tone mapping.

Exposure blending is the less complicated alternative. There are fewer options to concern ourselves with. The processing runs faster (although, it does require a lot more RAM). Noise tends to be less of a problem. I excluded exposure blending on an important technical ground: when the dynamic range is great, exposure blending tends to result in an image with less local contrast. In other words, the result tends to look flatter.

Working with HDR is a two-step process. The first step is easy enough. You load several exposures of the same subject in Photomatix Pro and select the option to generate an HDR image. This creates a 32-bit HDR imge that will be sure disappoint. A conventional monitor cannot display the wider dynamic range of an HDR image. Likewise, a convention printer cannot properly print them.

Here's a screen capture of the HDR image:

An HDR file is like a RAW file from a DSLR. It's not intended for viewing or printing. It requires additional processing. That's the tone mapping step. Before we go there, here's the settings I used for Lowell's exposures.

I'm not going to explain all of the features and options in Photomatix Pro. That's more appropriate for a forthcoming, comprehensive software review. Image alignment is important. Even with a tripod, there can be tiny movements. Chromatic aberrations (CA) will be most obvious in bright highlights. With multiple exposures pushing the highlights, it is a good idea to check for CA and correct it. Lowell sent me TIFFs instead of RAW files. The photos were in the AdobeRGB colorspace. I allowed Photomatix Pro to read the tone response curve from the embedded ICC profile in each TIFF.

When it comes to noise reduction, I decided to wait and see if it was an issue. If it was, I'm inclined to wait until I get to Photoshop and use a commercial plug-in like Neat Image or Noiseware to handle the problem. Again, not a ding at Photomatix. I use tools for their strengths. That means, I prefer noise reduction tools for reducing as much noise while sacrificing as little detail as possible.

Photomatix Pro includes a small preview window to give the user an indication of what the photo will look like after additional processing. I was generally pleased with the result. Just keep in mind, though, the preview is a rough guide. You'll be making several choices (unless you stick with the Photomatix defaults) and they will affect the final result..

Rght from the start, there's a big decision when it comes to tone mapping. Use the Details Enhancer or the Tone Compressor. It's either/or.

The Photomatix manual was obviously written by an engineer. Telling laymen that the Detail Enhancer is a local operator and the Tone Compressor is a global operator is to talk unintelligibly. What's the difference between a local operator and a global operatior?!

A global operator is the simpler mathemtical operation of the two. It applies the same adjustment to each pixel. It doesn't look at neighboring pixels and react accordingly. That means the Tone Compressor runs faster, since fewer calculations are involved.

Briefly, what's going on is this. The dynamic range of a 32-bit HDR image is too great for a conventional monitor or printer. So, to make a 16-bit or 8-bit photo, the dynamic range has to be compressed. It has to be made to fit within the dynamic range that conventional monitors and printers can handle. With a global operator, the same compression is applied to the entire photograph. With a local operator, a pixel is compared to its neighbors. If the pixel is surrounded by brighter pixels, a different compression is applied than what's applied to a pixel surrounded by darker pixels.

I chose the Tone Compressor for Lowell's photographs. It produces more "natural" looking results. Many of the HDR examples on the Web that look "over the top" were run through the Details Enhancer. You can get some interesting artistic effects by whacking around tonal ranges with the Details Enhancer.

There are a number of options for the Tone Compressor. I made two separate conversions. The first used the defaults and dropped the Brightness setting to -6. I did this to maximize the detail from the stained glass. I was going to use it ot make a composite of one HDR photograph with another. All I wanted was just the stained glass from this version.

Photomatix Pro has no built-in capacity to save multiple versions of a file. So, you have to accept the settings to make a tone mapped version of the file, save that, then drop the changes and make new settings choices. I'll ding Photomatix Pro for this. It's clumsy and assumes one tone mapped HDR photo will suffice.

The screen shot below is the settings I used for the primary tone mapped photo. I intended to use everything from this version except for the stained glass. I also used the Loupe to watch the details as I adjusted the Tone Compressor sliders.

Brightness was increased to +1. This increases or decreases the overall brightness of the image. Pull this up too much and noise will become more evident in the shadows. I kept it somewhat subdued, since I intended to do some adjustment to white balance and tone in Photoshop, where the controls are more flexible. Tonal Range Compression was also set to +1. Shifting it to the right increases compression, which means it shifts extreme shadows and highlights more towards the midtones. Contrast Adaptation affects the influence of average brightness on the pixel being processed. The practical result is this: large positive values mean more pronounced colors and negative values mean more natural looking colors. The White Point and Black Point settngs were critical for retaining fine details.

In a word, I was looking for a natural effect. I didn't want a hypersaturated photo that's popular with many HDR mavens. I'm not opposed to the look. It works great for many photographs. It just wasn't the effect I wanted for the interior shot of a church. I wanted more dynamic range, but I wanted a natural-looking result, too.

The result from the Tone Compressor was quite nice. It has more detail in both the shadows and the highlights than was possible with any single, isolated exposure.

The result also appears a little flat. A global reduction in contrast is common with tone mapped HDR. I took one brief look and was confident that a few, easy maneuvers in Photoshop would add plenty of "pop" to this photo.

I could have spent more time jimmying the Tone Compressor settings. You have to decide how to use your time efficiently when retouching. There are often several ways to accomplish the same or a similar result. Sometimes one or another is easier, less time-consuming, whatever. I was confident the settings I settled on had captured lots of dynamic range. I could give the gold more luster and enhance small details more easily in Photoshop, so that's where I took the two tone compressed HDR photos.

On To Photoshop

The first change I wanted to make, was to bring in even more detail to the stained glass. In most church interiors, the stained glass are an important feature. The eye is almost invariably drawn to it.

I opened both of the tone mapped HDR photos: the version that was the foundation for everything else and the version with maximum details for the stained glass. The stained glass version was the source. With both photos tiled, I selected the entire photo with the rich stain glass using alt/option + A and then being sure to hold down the shift key, I dragged it onto its destination. That left me with the stained glass version as a new layer above the photo I was going to adjust. Both versions were perfectly aligned.

A few minutes effort went into creating a mask to bring through only the details for the stained glass. There were lots of colors in the stained glass and I considered using the Color Range command. That would take too long. After a moment's thought, I decided to select the subdued background and then invert that selection. Getting most of the background would be easy with the Magic Wand and a large enough Tolerance setting.

I made a few stabs with the Magic Brush tool. That got most of the background. Then I inverted the selection

After a minute or two of clicking at small areas with marching ants, I decided to make the selection into a mask and then paint out any resistant areas with the Brush tool set to Black at 100% opacity.

I applied a one pixel Gaussian Blur to complete the mask. A slight blur helps to make smoother tranistions between masked and unmasked areas. I ctrl-clicked on the mask to make it an active selection. Then I added the selection as a layer mask by clicking on the little icon at the bottom on the Layers palette. You could also use selection Layer | Layer Msk | Reveal Selection to make the layer mask.

To check the mask, I temporariy added a Solid Fill adjustment layer filled with Black underneath the layer with the stained glass. Below is the result:

Simply copying over the stained glass left a result that looked artificial. The colors and details in the stained glass were too pronounced. Easily fixed. I backed off the Opacity for the layer to 60%. I also set the Layer Blend to Darker Color. What I was after were richer details and these settings gave me what I was looking for.

The rest of my effort focused on some global brightening, a healthy dose of global contrast to add luster to the gold, and some sharpening of photographic details.

I used a Levels adjustment layer to brighten the photo slightly and adjust the white balance with the gray and black eyedroppers. When the photo was brightened, I didn't want to lose detail in the stained glass, so I kept the Levels adjustment layer away from the stained glass by using the same mask I used for the previous layer. I just inverted the mask. You can see this in the Layer palette screen shot.

Some viewers might prefer a brighter church interior. That's easily accomplished. I decided to keep the appearance of natural lighting. Even with light streaming in through stained glass, a church is going to have subdued lighting. There's some German writing up near the ceiling. I added enough brightening to make it easily legible.

The Levels layer also has a feature that's not obvious. The Layer Blend was set to Soft Light. That's what gave the luster to the gold and also added "pop" to colors inside the church. The layer's Opacity was set to 60%. You could substitute Overlay for some more "pop" or Hard Light for more yet.

Fine details were given additional sharpness and some further contrast was added to those details with High Pass sharpening. That meant duplicating the visible pixels to a new layer, converting that to a Smart Filters layer, adding an Overlay blend, and then invoking the High Pass filter with a Radius setting of 4.1 pixels.

I wanted to keep the High Pass sharpening away from the brightest highlights. After all, I worked hard to retain detail in the stained glass. It was easy to blow it out again. To keep the High Pass filter sharpening away from the highlights, I used the Underlying Layer Blend If slider. I split the highlights slider at 192 and 224 for a smooth transition.

The final steps were to prepare the photo for printing. I reduced the size to 12 inches x 8 inches at 240 ppi. Then I used the TLR Inkjet Output Sharpener with settings of 240 ppi glossy.

The result is a very lovely print. The stained glass windows have lots of detail. The interior of the church does, too. The small version here does not do full justice to the full-size photo.

Photomatix Pro is an excellent tool for combining multiple exposures. No single exposure, even with current generation DSLRs, can capture all of the dynamic range in this photograph.

A .PDF of this coaching session is available for download by clicking here . . .